Electrospray ionization (ESI) is a technique used in mass spectrometry to produce ions using an electrospray in which a high voltage is applied to a liquid to create an aerosol. It is especially useful in producing ions from macromolecules because it overcomes the propensity of these molecules to fragment when ionized. ESI has important applications in mass spectrometry, propulsion, and materials fabrication.
As mentioned above, in ESI, electrical contact with a voltage supply is necessary to generate a continuous spray of charged droplets from a sample solution. The electrical contact adds dead volume and adsorption surfaces, requiring cleaning to eliminate sample carryover. Electrical contact also complicates the apparatus configuration, especially for arrays of ESI emitters.